German publication DE-C 11 72 157 discloses an incendiary splinter projectile comprising a hollow inner container with a coating of pre-fabricated individual splinters thereon and an outer casing; these splinters are metallic bodies having on their surface a coating of a pyrophoric material, preferably of a possibly alloyed pyrophoric metal, the pyrophoric properties becoming effective upon impact on the target. These splinters (splinter-active components) are embedded in a synthetic resin composition. The pyrophoric metal coating on the surface of the splinter-active component (construction splinters) consisting of metal, such as steel, is preferably selected from the group consisting of aluminium, magnesium, zirconium, titanium and pyrophoric alloys made therefrom. This publication does however not contain any details about specific steps as to the application of the respective pyrophoric coating onto the surface of the splinter-active component. German publication DE-A 31 11 725 relates to a fuseless ring blade projectile. The tubular projectile body of this projectile has either along its outer lining or preferably along its inner lining breaking points caused by structural weakening. Such a pre-fragmentation of the projectile casing provides splinter-active components programmed as to size, shape and number. The necessary structural weakening of the projectile casing may be achieved e.g. through milling and lathing operations or through treatment with electron beams or ion beams. In its pre-fragmented range, the projectile casing thus provided with breaking points comprises a coating of a filler having a form sufficient stable to guarantee a smooth surface; it is advantageous if this coating consists of a material or a material composition having pyrophoric properties. If such a projectile casing (splinter-active component) is destroyed, there are formed fragments or splinters of the desired size, shape and number which do not only penetrate inflammable targets, such as fuel tanks, but also set them on fire on account of the pyrophoric surface coating. This publication does not contain any details as to the material or material composition having pyrophoric properties. Furthermore, this publication leaves completely open by which exact steps such a pyrophoric coating can be applied to the surface of the splinter-active component (tubular projectile body) of the respective ring blade projectile (incendiary splinter projectile).
The German publication DE-A 32 45 904 discloses a thin-walled tubular projectile having incendiary properties. A relatively thin coating of an easily castable and curable incendiary composition containing an organic binder is applied to the inner lining of the projectile casing. This publication and the German publication DE-A 31 11 725 already discussed before do not contain any details about the kind and the composition of the incendiary pyrophoric coating of this tubular projectile. However, the use of a castable and curable incendiary composition containing an organic binder means that the pyrophoric component is present in pulveralent form, be it as one single material or as material composition. Consequently, one cannot conclude from this publication that there is a pyrophoric compact metallic coating along the inner lining of the casing of this tubular projectile even if the pulverulent pyrophoric component were based upon cerium misch metal.
The German publication DE-A 20 59 753 discloses incendiary splinter projectiles and other incendiary splinter weapons whose splinter-active components which are e.g. projectile casings made of steel, hard metal or heavy metal, casings or other weapons or other construction splinters have a pyrophoric coating of a compact metallic alloy having pyrophoric properties on their surfaces or on parts thereof, the major component of this coating being a rare earth metal. Preferably, this rare earth metal consists of cerium misch metal containing at least 45 wt.-% of cerium. Such an alloy may contain as additional metals e.g. iron, titanium, copper, beryllium antimony, tin, zinc, lead and aluminum in subordinate amounts in order to improve the disruptive strength of the pyrophoric coating. Furthermore, it is advantageous if the alloy on the basis of cerium misch metal also contains magnesium in an amount of less than 5 wt. %; this in order to prevent an oxidation and in order to improve the incendiary properties of the coating. Furthermore, the alloy on the basis of cerium misch metal is to contain preferably a relatively high amount of iron, e.g. 12.5 wt. %, in order to retard the burn-up speed of the coating in a controlled manner, and first of all to contain a certain minimum amount of carbon, e.g. of 0.035 to 0.085 wt.-% in order to improve the extensibility of the coating. The production of the alloy required for the preparation of a pyrophoric coating is, in the usual manner, effected by melting the components and subsequently solidifying the fused mass both in an inert atmosphere; in case of the intentional addition of carbon, the fused mass is annealed until the desired maximum carbon amount is obtained. The application of a pyrophoric coating consisting of such an alloy is effected e.g. by coating the either mechanically, through abrasives, or chemically, through etching agents, cleaned surface of the splinter-active component with a molten alloy, by solidifying the coating and possibly by tempering the coated component, these method steps being carried out in an inert gas atmosphere. By the possible tempering step, the adhesion of the pyrophoric coating to the surface Of the splinter-active component is to be additionally improved through a so-called diffusion bond. In order to attain this effect, the coated component is held over a longer period of time in an inert gas atmosphere at a temperature lower than the melting temperature of the respective alloy and being suitably close to this temperature. Consequently, the tempering step will have to be carried out at a temperature allowing a diffusion of the metallic components of the neighbored surfaces without entailing the risk of a melting of the solidified coating.
In order to attain an additional improvement of the desired diffusion bond, this operation is suitably carried out under pressure by subjecting the composite body (splinter-active component) carrying the pyrophoric coating to a suitable pressure. Another possibility of applying a pyrophoric coating consisting of an alloy on the basis of cerium misch metal to the surface of the respective splinter-active component is to be seen in the feature that prefabricated compact bodies are used as coating which is applied to the surface of the respective splinter-active component only through diffusion bonding, this requiring practically absolutely the simultaneous employment of pressure in order to yield a sufficiently stable bond. Also such a method is again effected in an inert gas atmosphere. The afore-mentioned two methods involve however the disadvantage that the steps to be taken are very expensive, require high processing temperatures and do not yield uniform coatings. Furthermore, the coating with prefragmented splinter-active components entails the disadvantage that the recesses required for a fragmented destruction are completely occupied by the alloy applied in its molten state. In this way, the effect desired from a pre-fragmentation gets partially lost. A subsequent fragmentation of the coating is possible, however it is rather expensive. In the separate production of compact bodies of the pyrophoric coating one may provide for the desired prefragmentation through the use of corresponding molds, however, such pre-fabricated bodies may be applied to the surface of the respective splinter-active component only through diffusion bonding (or e.g. also through sticking). Therefore, the adhesion of the coating bodies onto the surface of the splinter-active component is insufficient.
The German publication DE-A 37 25 091 relates to an incendiary splinter projectile wherein the inner lining of the projectile casing is locally limitedly coated with an incendiary composition by leaving free lattice-structured spaces and wherein the explosive within the interior of the projectile casing extends also into the uncoated lattice-structured spaces. The lattice-structure is formed through placement of a curable and removable auxiliary material corresponding to the respective desired structure. This auxiliary material is suitably a specific matrix which can be applied to the inner lining and which can be removed afterwards; the spaces of this matrix are filled with the respective incendiary composition when the desired pyrophoric coating is applied. This incendiary composition may be any infiltratable incendiary composition which is preferably based upon an alloy of zirconium and titanium and is particularly a cerium misch metal. It is introduced according to a centrifugal casting process and is thus applied in its molten state as a coating to the inner lining of the projectile casing of the respective splinter projectile. By the employment of a matrix, it is possible to apply the pyrophoric coating to the inner lining of the casing of an incendiary splinter projectile by leaving free desired lattice-structured spaces which may also correspond to structural weakenings or pre-fragmentations of the projectile casing. The required specific matrix renders this method however rather expensive. The necessity of the application of the coating according to the centrifugal casting method involves in turn the disadvantage of a very compact pyrophoric coating e.g. of cerium misch metal whose ignition and through-reaction is not safeguarded when coming into use. Furthermore, this method does not allow a uniform coating having a smooth surface; consequently, a subsequent treatment, e.g. lathing treatment, of the coating obtained according to the centrifugal casting method might become necessary.
The known methods of applying a coating of cerium misch metal to the splinter component of an incendiary splinter projectile, and particularly the methods of applying the fused mass coating possibly with diffusion bonding of the coating through a tempering step involve the considerable disadvantage that the thus obtained adhesion of the coating to the surface of the respective splinter component is not sufficient in many cases. Due to the involved forces, the use of such incendiary splinter projectiles results therefore in a separation of the coating from the carrier, viz. from the splinter component; so the splinter component will be inactive and will no longer have an incendiary effect because the fragments of the coating alone do in general not have sufficient properties to break through the respective target. Furthermore, the known methods are relatively expensive, require in general high processing temperatures and do not allow the formation of a uniform coating following the configuration of the splinter component. Therefore, there are required subsequent treatments in order to obtain at least a smooth surface. The structural weakenings or recesses possibly provided at the carrier and required for a fragmented destruction of the respective splinter-active component are, according to most of the known methods, generally completely filled with pyrophoric material. Therefore, the effect of the pre-fragmentation is totally or at least partly cancelled unless this is prevented in advance by expensive additional measures or if no suitable subsequent treatment of the coating is effected.
It is therefore the object of the present invention to provide an improved method of applying a pyrophoric cerium misch metal coating to the surface of a splinter component of an incendiary splinter projectile and to overcome the afore-mentioned disadvantages of the known methods. Hence, the object of-this method is to provide a firmly adhering and easily ignitable coating which is not too expensive, which does not require high processing temperatures and which has a uniform thickness and a smooth surface, so that no subsequent treatments, especially also with respect to a restoration of the contours of the pre-fragmentation, will be necessary. The present method is to improve known methods wherein the respective coating of a fused mass of cerium misch metal is applied.